lie about futex_atomic_cmpxchg_inatomic kernel support.
In past versions of glibc, we incorrectly assumed all ARM kernels
in all configurations supported futex_atomic_cmpxchg_inatomic. This
was clearly a lie, however it was a lie that we relied on, because
the fallback implementation appears to not play nicely with certain
applications like pulseaudio. Restore the lie for kernels > 2.6.32
and plug our ears and scream "LA LA LA" about how wrong this is.